Uveal melanoma (UM) is the most common primary cancer of the eye with over 50% of patients developing metastatic disease, which is notoriously resistant to chemo- and immunotherapy. UMs can be categorized by gene expression profiling (GEP) into two molecular classes associated with metastatic risk using a clinically available prognostic test: Class 1 (low metastatic risk) and Class 2 (high metastatic risk). The Class 2 signature is strongly associated with inactivating mutations in the BAP1 tumor suppressor gene. Though most patients that metastasize have a Class 2 GEP, a percentage of Class 1 patients also metastasize. We have identified a new subtype of UM that is characterized by a Class 1 GEP and high PRAME expression (Class1PRAME+) that has an increased risk of developing metastasis (intermediate metastatic risk). In our data set, the 5-year actuarial rate of metastasis was 0% for Class1PRAME- tumors, 38% for Class1PRAME+ tumors, and 71% for Class 2 tumors (with similar findings in independent validation data sets). Our preliminary studies show that PRAME overexpression in UM cell lines promotes aggressive and deadly metastases in a xenograft animal model. The first aim of this proposal is to examine the molecular interactions of PRAME in UM in order to shed light on how PRAME is promoting metastasis. Identification of binding partners and molecular interactions will help identify potential therapeutic strategies for Class1PRAME+ patients. The second aim is focused on studying genetic and transcriptional alterations that are present in PRAME overexpressing cells and tumors. Potential transcription factors that regulate these alterations will also be explored. Finally, this aim will explore genetc mutations in Class1PRAME+ tumors that may promote metastasis and/or trigger PRAME overexpression. Completion of this proposal will likely provide therapeutic targets that can be used to stratify UM patients into adjuvant clinical trials with the goal of improving outcome and finding a treatment for this deadly cancer.